The present invention is a laminated wood product for use where good appearance and dimensional stability are of paramount importance. The product is particularly useful for stiles and rails of paneled doors where it gives the appearance of high grade solid sawn lumber. The product is further characterized by excellent dimensional stability and freedom from warpage.
The availability of good appearance grade lumber products is becoming poorer and poorer as the last of the available old growth western timber is being harvested. Forest products manufacturers have responded to this problem in a number of ways, one of which has been the import of tropical woods. Another way has been to end and/or edge joint smaller pieces of wood into larger standard size units. Both of these approaches have problems in their own right. The clear wide lumber cut from tropical trees is expensive, often lacking in desirable or necessary physical properties, and tends to have a very bland grain pattern. The edge and end glued products lack continuity of grain pattern so that it is almost essential for them to be finished in opaque paints. Very often, despite the best care during manufacture, the joints themselves will also telegraph through the painted surface. A third approach has been the lamination of a number of pieces of wood so as to simulate a single piece of solid sawn lumber. The use of laminated lumber of this type appears to be especially directed to stiles and rails for paneled doors. Until now this application has required clear lumber of the highest quality.
One laminated wood product of the type noted above, while not intended for use in door stiles, is shown in FIG. 2 of Clark, U.S. Pat. No. 3,445,325. Turner, in U.S. Pat. Nos. 4,702,054 and 4,704,834, shows a rather complex paneled door in which the stiles, rails, and panels are all made of laminated members intended to simulate solid wood. The stiles and rails are strips applied to both faces of a plywood core which is coextensive over the entire area of the door. The openings around the panels are edged in decorative moldings and all of the raised surfaces may be covered with a thin wood veneer. This door is said to be more secure, fire tight, and less resistant to separation and loosening of the panels. As described in the patent, a standard six-panel door would require 79 individual pieces of wood without even considering the face veneers.
Hagemeyer, in U.S. Pat. No. 4,716,700 describes what he calls "plantons." These are add-on panels to give a flush door the appearance of a panel door. The portions simulating stiles and rails, perhaps best seen in FIGS. 8 and 9, are complex constructions of cross banded veneers which also include an aluminum vapor barrier. As seen in FIG. 8, in some locations the construction comprises at least 13 individual laminae.
The above-noted door constructions should be compared with a standard six-panel door which is made of 15 individual pieces of wood. These are already considered by most wood workers to be of complex and expensive construction.
As the availability of high grade solid wood for stiles and rails decreases, so does the quality. Much of the material available now is from second growth trees which tend to have much more widely spaced annual rings than old growth timber. This wood is undesirable from two standpoints, one aesthetic and one functional. Most door stiles and rails are made of vertical or edge grain lumber; i.e., lumber cut generally along a radius of the log. Second growth lumber is more normally available only in flat grain or generally tangentially sawn lumber and its appearance is not as highly regarded. The second growth lumber has a more serious problem, however. It has a much greater tendency toward warpage than lumber from old growth logs. This warpage is usually manifested in one of three ways. These defects are known as twist, bow, and crook. Frequently some combination of these warpage defects is present.
Twist is a warpage defect which can be best visualized by imagining the shape a piece of lumber would assume if each end was tightly grasped and then twisted in opposite directions. Stated otherwise, the board tends to assume the configuration of a portion of a spiral.
In lumber with bow, the edges lie on parallel planes but the faces are curved. When laid on one of its faces, bow causes the lumber to be shaped like the rocker of a rocking chair.
Crook is deviation from linearity of the edges of a piece of lumber when it is laid on one of its widest faces and is warpage 90.degree. displaced from bow. A piece of lumber having only crook will have the faces lying in parallel planes with the edges curved.
While grading rules set limits for warpage, a piece that is satisfactory at one moisture content may show unacceptable warpage at a slightly different moisture content. This problem, along with availability, presents a serious challenge to door manufacturers who wish to supply a quality product.
A further problem might be noted with some of the laminated structures described earlier. Very often the end grain of the various laminae are apparent either along the edges of the door itself or along the molded areas adjacent to the interior panels. While this does not necessarily detract from the performance of the doors, it is a feature which has met with considerable consumer resistance since it is visually unaesthetic.
The present invention is a lumber product which appears to overcome most or all of the above-noted objections, including the problems of appearance in laminated products and warpage in solid wood products.